Sediments associated with Mississippi rivers and lakes contain significant
concentrations of environmental contaminants including pesticides and industrial
by-products. Chemical characterization of these complex mixtures is often
expensive and incomplete. Certain cytochrome P450 enzymes such as CYP1A have
been developed as biomarkers of exposure in fish and wildlife. These physiological
endpoints integrate exposure to several types of contaminant, are cheaper
than analytical analyses, and are indicative of bioavailable contaminants.
Biomarker methodologies are critical in order to detect toxic insult at sublethal
exposures so that individuals, population and community structure are not
affected by contamination of Mississippi waterways. This project is specifically
aimed at characterizing the utility of a recently discovered cytochrome, CYP1B1,
as a marker of exposure to contaminants that have been reported by the USGS
NAWQA and BEST programs in Mississippi sediments and fish samples. Because
channel catfish are such an abundant and economically significant species
in Mississippi, they will be used as the test organism in these studies.

Using primary cultured channel catfish liver hepatocytes to screen a series
of diverse contaminants including polychlorinated biphenyls, polycholorinated
dibenzo-p-dioxins, polycyclic aromatic hydrocarbons and organochlorine pesticides,
the inducibility and/or inhibition of CYP1B1 will be tested. For compounds
that indicate in vitro inducibility, we will conduct in vivo exposures to
characterize the in vivo time course and dose response relationships in channel
catfish. Ultimately, we will characterize the in situ utility of CYP1B1 as
a biomarker of exposure to contaminated sediment in channel catfish collected
from Mississippi lakes and rivers. This project has the potential to develop
an entirely new physiological endpoint of contamination in fish. Because of
its role in carcinogenesis, insight into the mechanisms of CYP1B1 induction
across taxa will be a significant advance toward applications of CYP1B1 status
as a marker for environmental contaminants and potentially cancer.